Super-capacitive carbon and method for its production

Abstract

The application provides a supercapacitor carbon and a preparation method thereof. The preparation method comprises the following steps: firstly, mixing petroleum coke and pitch uniformly to obtain a first material; then, carbonizing the first material under the condition of an oxygen-containing gas to obtain a second material; then, crushing the second material and mixing the second material with alkali to perform primary activation under an inert atmosphere to obtain a third material; then, washing and drying the third material, mixing the third material with pitch and alkali, and performing secondary activation under an inert atmosphere; finally, washing and drying to obtain the supercapacitor carbon. The supercapacitor carbon has mesopore-micropore two-stage pore channels, wherein the mesopore has a pore diameter of 2nm-5nm, and the micropore has a pore diameter of 0.4nm-2nm. The application realizes the short-range through-hole pore channel structure design of the petroleum-based porous material through a combined process, provides a large specific surface area for the formation of an effective double electric layer, guarantees the rapid transmission of electric charges, and significantly improves the long-period cycle stability of the material.

Description

Technical Field

[0001] This invention belongs to the field of carbon materials technology, and relates to supercapacitor carbon and its preparation method, particularly to a petroleum-based supercapacitor carbon and its preparation method. Background Technology

[0002] Currently, new energy sources such as photovoltaics and wind power are in a period of rapid development, and the energy storage industry, as a crucial supporting link, is also making great strides. New energy storage technologies are constantly emerging and rapidly entering the market, and are expected to play a pivotal role in the energy storage field in the future. The energy storage industry is about to usher in its golden age.

[0003] Among various energy storage devices, supercapacitors have significant advantages. Lithium-ion batteries convert electrical energy into chemical energy, and then back into electrical energy during use, resulting in energy loss during this secondary conversion process. Their current efficiency is typically only about 70-80%. Supercapacitors, on the other hand, store electrical energy as charge within the device through an electric double layer, unlike lithium-ion batteries which involve energy conversion. Their charge-discharge efficiency can reach over 98%. This results in superior reversibility and extremely fast response. Compared to the currently rapidly developing lithium-ion batteries, supercapacitors can have a power density 30 to 100 times higher. Supercapacitors feature fast charge-discharge speeds, high power density, a cycle life of up to one million cycles, adaptability to harsh environments, and minimal maintenance requirements. They have immeasurable application prospects in electric vehicles, urban rail transit, auxiliary power supplies for solar and wind power generation systems, military and aerospace applications, and industrial backup power supplies.

[0004] There are two types of charge storage mechanisms in supercapacitors: one is based on the electric double-layer capacitor at the electrode-electrolyte interface with a high specific surface area, and the other is based on pseudocapacitive capacitors related to rapid surface redox reactions of metal compounds, conductive polymers, and carbon materials doped with heteroatoms. Supercapacitors using carbon materials as electrodes are electric double-layer capacitors. Their energy storage principle involves the adsorption of pure electrostatic charges on the electrode surface to generate stored energy. During charging and discharging, the polarized electrode surface attracts oppositely charged ions from the electrolyte solution, causing these ions to attach to the electrode surface and form an electric double-layer capacitor, thereby generating a stable potential difference between the positive and negative electrodes.

[0005] Electrode materials are crucial for supercapacitors, determining their main performance characteristics. Porous carbon materials, with their high specific capacitance, long cycle life, abundant resources, diverse structures, and moderate cost, are the most active research area in the field of supercapacitors. Currently, there is a consensus that carbon materials must meet several stringent requirements, including large specific surface area, reasonable pore size distribution, high purity, and high packing density, to achieve their advantages such as high energy density, high power density, and long service life.

[0006] The relationship between the microstructure of carbon materials and their capacitance performance is complex. Specific surface area, internal resistance, pore size distribution, surface functional groups, and ash content all affect the capacitance performance of the material. However, currently commercially available supercapacitors using carbon materials are still predominantly microporous with a low content of mesopores. This results in fewer effective electric double layers that can be formed in the microporous structure, leading to low utilization of the pore structure. Consequently, the materials have high internal resistance, low specific capacitance, and poor rate performance. Furthermore, the presence of heteroatoms and functional groups on the surface of carbon materials significantly impacts their mechanical and electrochemical properties, particularly hindering rate performance and long cycle life. To improve the conductivity, specific capacitance, and other properties of composite carbon materials, carbon nanotubes, graphene, and heteroatom doping are widely used in their construction.

[0007] Patent 106115694 A directly performs high-temperature coking reduction and activation on graphene oxide and pitch coke, so that graphene forms a conductive network inside the activated carbon, which changes the problem of high internal resistance of pitch-based activated carbon. However, the improvement effect is not obvious when the amount of graphene added is small. Increasing the amount of graphene added will significantly increase the cost of the composite material. Moreover, the graphene oxide and pitch coke need to undergo repeated high-temperature mixing processes in the early stage to ensure the uniformity of the conductive network in the composite material.

[0008] Patent CN 109665523 A uses a combination of chemical reduction, hydrogen peroxide etching, and high-temperature reduction to prepare graphene-based petroleum coke-based activated carbon. However, this process is not only expensive in terms of raw materials, but also requires a complex preparation process to achieve good contact and uniform mixing between graphene and petroleum coke. It is evident that the contact and bonding ability between graphene oxide and petroleum coke is not good. Therefore, it is not advisable to improve the structure of the composite material by adding graphene during industrial scale-up.

[0009] It is evident that the construction methods of composite carbon materials such as carbon nanotubes, graphene, and heteroatom doping often suffer from drawbacks such as high cost, complex preparation processes, and poor material mechanical properties. Although they can improve the specific capacitance and conductivity of carbon materials to some extent, they are detrimental to improving their rate performance and long-cycle performance.

[0010] Therefore, obtaining a capacitor carbon material with a more reasonable pore structure distribution and better surface chemical properties, and improving its long-cycle performance, is of great significance for promoting the development of supercapacitors and the practical application of activated carbon materials. Summary of the Invention

[0011] To overcome the aforementioned problems in the prior art, this invention provides a supercapacitor carbon and its preparation method. Through a combination of oxidation carbonization-primary activation-secondary activation processes, the short-range through-pore pore structure design of petroleum-based porous materials is achieved, providing a huge specific surface area for the formation of an effective double layer, ensuring rapid charge transport, and significantly improving the long-term cycling stability of the material.

[0012] The first aspect of this invention provides a method for preparing supercapacitor carbon, comprising the following steps:

[0013] (1) The first material is obtained by mixing petroleum coke and first bitumen evenly;

[0014] (2) In the presence of oxygen-containing gas, the first material obtained in step (1) is processed to obtain the second material;

[0015] (3) After crushing the second material obtained in step (2), mix it with alkali and perform a first activation under an inert atmosphere to obtain the third material;

[0016] (4) The third material, alkali and second pitch obtained in step (3) are mixed and activated twice under an inert atmosphere. After washing and drying, supercapacitor carbon is obtained.

[0017] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the particle size of petroleum coke in step (1) is 10-500 μm, preferably 20-100 μm; the volatile content in petroleum coke is 5wt%-15wt%, preferably petroleum coke containing a fine mosaic structure.

[0018] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the first bitumen in step (1) is one or more of petroleum bitumen and coal bitumen, preferably petroleum bitumen; the softening point of the first bitumen is 80-350℃, preferably 100-300℃.

[0019] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the weight ratio of the first pitch to petroleum coke in step (1) is 1:20 to 1:0.1, preferably 1:10 to 1:0.2.

[0020] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the mixing in step (1) can be carried out by any of the existing methods that can achieve uniform mixing of solid materials, specifically by mechanical mixing, crushing, shearing, ball milling, etc.

[0021] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the volume fraction of oxygen in the oxygen-containing gas in step (2) is 0.5% to 21%, preferably 1% to 15%. The oxygen-containing gas is air and / or a mixture of oxygen and an inert atmosphere, and the inert atmosphere can be any one or more of nitrogen, helium, neon, argon, krypton, and xenon. The flow rate of the oxygen-containing gas is 50 to 500 mL / min, preferably 100 to 300 mL / min.

[0022] Furthermore, in the above method for preparing supercapacitor carbon, the processing time in step (2) is 20 to 200 min, preferably 60 to 120 min.

[0023] Furthermore, in the above method for preparing supercapacitor carbon, the processing temperature in step (2) is 80-350℃, preferably 100-300℃; and the heating rate is further controlled to be 1-20℃ / min, preferably 5-15℃ / min.

[0024] Furthermore, in the above method for preparing supercapacitor carbon, the particle size of the second material obtained in step (2) after pulverization is 10-500 μm, preferably 20-200 μm.

[0025] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the alkali in steps (3) and (4) can be one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate, calcium hydroxide, and magnesium hydroxide, preferably one or more of sodium hydroxide, potassium hydroxide, and potassium carbonate.

[0026] Furthermore, in the above method for preparing supercapacitor carbon, the alkali in steps (3) and (4) is a particulate solid with a particle size of 10 to 300 μm.

[0027] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, before the activation treatment in steps (3) and (4), an inert atmosphere is usually used to fully replace the gas in the activation device to ensure that there is no oxygen in the activation device.

[0028] Furthermore, in the above method for preparing supercapacitor carbon, the initial activation temperature in step (3) is 700-1000℃, preferably 700-900℃; furthermore, the initial activation heating rate is 1-10℃ / min, preferably 2-8℃ / min; and the initial activation time is 20-120 min, preferably 20-100 min.

[0029] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the weight ratio of the second material to the alkali in step (3) is 1:0.2 to 1:10, preferably 1:0.5 to 1:2.

[0030] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the washing in step (4) includes two washing operations: acid washing and water washing. The main purpose is to remove the alkaline substances produced by the reaction through acid washing and water washing, thereby exposing the rich pore structure formed during the activation process. Generally, water washing involves washing several times with deionized water or ultrapure water. During water washing, the liquid-solid mass ratio of water to solid material is 10:1 to 50:1, preferably 10:1 to 30:1. The acid solution used in the acid washing process can be one or more of hydrochloric acid, nitric acid, sulfuric acid, and acetic acid. The mass fraction of the acid solution is 0.5% to 20%, preferably 1% to 10%. The liquid-solid mass ratio of the acid solution to the solid material is 5:1 to 30:1, preferably 5:1 to 20:1.

[0031] Furthermore, in the above method for preparing supercapacitor carbon, the drying temperature in step (4) is 60-150℃, preferably 60-120℃; the drying time is 1-24h, preferably 4-12h.

[0032] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the second asphalt in step (4) is one or more of petroleum asphalt and coal tar pitch, preferably petroleum asphalt; the softening point of the second asphalt is 80-200℃, preferably 80-180℃; the softening point of the second asphalt is 50-250℃ lower than that of the first asphalt, preferably 100-200℃ lower; the content of metal impurities in the second asphalt is 20-300 ppm, preferably 30-200 ppm.

[0033] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the weight ratio of the second pitch to the first material in step (4) is 1:13 to 1:2, preferably 1:10 to 1:3.

[0034] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the secondary activation temperature in step (4) is 500-900℃, preferably 600-800℃; the heating rate of the secondary activation is generally controlled at 1-5℃ / min, preferably 2-5℃ / min; and the secondary activation time is 20-100 min, preferably 20-60 min.

[0035] Furthermore, in the above-mentioned method for preparing supercapacitor carbon, the weight ratio of the second pitch to the alkali in step (4) is 1:0.2 to 1:10, preferably 1:0.2 to 1:2.

[0036] A second aspect of the present invention provides a supercapacitor carbon, which is obtained by the above-described preparation method.

[0037] Furthermore, in the aforementioned supercapacitor carbon, the supercapacitor carbon has two levels of pores: mesopores and micropores. The mesopore diameter is 2nm-5nm, and the micropore diameter is 0.4nm-2nm. More specifically, the mesopore volume accounts for 12-25% of the total pore volume, and the micropore volume accounts for 75-88% of the total pore volume.

[0038] Furthermore, in the aforementioned supercapacitor carbon, the specific surface area of ​​the supercapacitor carbon is 200-3300 m². 2 / g, preferably 1500-2500m 2 / g.

[0039] Furthermore, in the above-mentioned supercapacitor carbon, the metal content of the supercapacitor carbon is not greater than 300 ppm, preferably not greater than 200 ppm.

[0040] Compared with existing technologies, the beneficial effects of the supercapacitor carbon and its preparation method provided by this invention are reflected in the following aspects:

[0041] (1) In the preparation method of supercapacitor carbon of the present invention, petroleum coke and asphalt are first mixed evenly and then oxidized and carbonized. During the carbonization of asphalt, the oxygen content and flow rate in the oxygen-containing gas are controlled to achieve weak oxidation of carbon atoms on the surface of petroleum coke and asphalt. After the oxidative carbonization treatment, the surface of the second material obtained is rich in oxygen-containing functional groups (including but not limited to carbonyl, carboxyl, ether bond, aldehyde, ketone, acid anhydride, etc.).

[0042] (2) In the preparation method of supercapacitor carbon of the present invention, the active oxygen-containing functional groups on the surface of the second material obtained after oxidative carbonization treatment become active sites during the alkali activation process, forming an active network on the surface of the second material. Compared with the untreated inert and dense petroleum coke surface, the efficiency of the alkali activation process is greatly improved, the chemical reaction between alkali and carbon matrix is ​​promoted, the formation of rich pore structure is beneficial, the activation depth can be increased, and the amount of alkali used can be significantly reduced.

[0043] (3) In the preparation method of supercapacitor carbon of the present invention, the carbon is constructed by using the difference in the activation degree of the two by the mixed oxidation carbonization and reactivation of petroleum coke and pitch. The carbon exhibits a micropore-mesopore ladder structure in the radial direction, which is conducive to the formation of short-range through-holes and thus more conducive to the rapid transport of electrons and ions.

[0044] (4) In the preparation method of supercapacitor carbon of the present invention, on the basis of obtaining activated carbon by one activation, a thin layer is coated on the outer surface of the activated carbon by a secondary activation method, and the thickness of the coating layer is controlled to wrap the heteroatom functional groups that may remain in the high-temperature thermal activation process in the carbon skeleton, so that they are no longer exposed on the carbon surface. The carbon surface after the thin layer coating treatment becomes inert again, which can significantly reduce the leakage current of the capacitor carbon and improve its reversibility and service life.

[0045] (5) The present invention realizes the pore structure design of short-range through-pores in petroleum-based porous carbon materials through a combination process of oxidation carbonization, primary activation and secondary activation, which provides a huge specific surface area for the formation of an effective double electric layer, ensures rapid charge transfer, and at the same time, the modulation of the surface structure significantly improves the long-term cycle stability of the material. Attached Figure Description

[0046] Figure 1 This is a pore size distribution diagram of the supercapacitor carbon sample obtained in Example 1 of the present invention. Detailed Implementation

[0047] The technical solution and implementation effects of the present invention will be further illustrated below with reference to specific embodiments and comparative examples, but are not limited to the following embodiments.

[0048] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0049] In this document, percentages and percentage contents are all expressed by mass unless otherwise expressly stated.

[0050] In this paper, the specific surface area and pore size distribution curves of the samples were obtained using nitrogen adsorption-desorption curves on a Micromeritics ASAP 2020 adsorption instrument at an operating temperature of -196℃ (liquid nitrogen temperature). The samples were pretreated for dehydration at 300℃ under nitrogen protection before testing. The specific surface area and pore size distribution were calculated using the BET and DFT methods, respectively.

[0051] The properties of the petroleum coke feedstock used in the embodiments and comparative examples of the present invention are as follows: sulfur content of 4.15 wt%, volatile matter of 15.79 wt%, and ash content of 0.79 wt%.

[0052] In this embodiment of the invention, the first asphalt has a softening point of 275°C and a toluene-insoluble content of 68 wt%; the second asphalt has a softening point of 155°C and a metallic impurity content of 56 ppm.

[0053] In this paper, the electrochemical testing method is as follows: Activated carbon, conductive agent acetylene black, and binder PVDF (polyvinylidene fluoride) are mixed evenly in a mass ratio of 8:1:1, coated onto carbon-coated aluminum foil, dried, sliced, and assembled into an organic coin-type supercapacitor. The electrolyte is 1 mol / L tetraethylammonium tetrafluoroborate dissolved in propylene carbonate. Then, electrochemical performance and long-cycle performance tests are performed on a Xinwei electrochemical testing instrument (model BTS-5V50mA).

[0054] Example 1

[0055] Weigh 10 g of petroleum coke and 2.5 g of first pitch and crush them to a particle size of 30 μm. Grind them in an agate ball mill jar for 100 min, load them into a corundum boat, place them in a carbonization furnace, and introduce a mixed gas of oxygen / N2 (oxygen volume fraction of 1%) at a gas flow rate of 200 mL / min. Heat the gas to 215 °C at a heating rate of 5 °C / min and perform oxidation carbonization treatment for 120 min. Allow the gas to cool naturally to room temperature (25 °C, the same below), remove it, and crush it to a particle size of 30 μm to obtain the second material.

[0056] The second material was mixed evenly with 25g KOH, placed into a corundum boat, and put into an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 500mL / min for 20min. Then, the temperature was increased to 900℃ at a nitrogen flow rate of 500mL / min and kept constant for 20min. The heating was then turned off, and the material was cooled to room temperature and taken out as the third material.

[0057] Weigh 1.8g of second asphalt and 3.0g of KOH, mix them with the third material, and pulverize them together to a particle size of 30μm. Then, ball mill the mixture in an agate ball mill jar for 30 minutes. The mixture is then placed in a corundum boat and placed in an activation furnace. The air in the activation furnace is replaced with nitrogen at a flow rate of 500mL / min for 20 minutes. The temperature is then increased to 700℃ at a nitrogen flow rate of 500mL / min and maintained at this temperature for 30 minutes. The heating is then turned off, and the mixture is cooled to room temperature. This is the final activated product. The product is then filtered and washed with a 5% (w / w) dilute hydrochloric acid solution at a liquid-to-solid mass ratio of 15:1. The filtered product is then washed with ultrapure water at a liquid-to-solid mass ratio of 40:1. The resulting filter cake is dried in a 120℃ forced-air drying oven for 6 hours to obtain porous carbon. The porous carbon is ball-milled to a D50 of 6–10μm and then subjected to magnetic separation to remove excess metal ions, yielding petroleum-based supercapacitor carbon.

[0058] The petroleum-based supercapacitor carbon prepared in Example 1 was analyzed and tested, and its specific surface area was 2306 m². 2 / g, particle size distribution D50 is 7.5μm, micropores account for 78%, mesopores account for 22%, and metal impurities are <200 ppm.

[0059] Electrochemical testing showed that the device's specific capacitance was 44 F / g at a current density of 1 A / g, and the specific capacitance retention rate was 87% after 100,000 charge-discharge cycles.

[0060] Example 2

[0061] Weigh 20g of petroleum coke and 2g of first pitch and crush them to a particle size of 40μm. Then, ball mill them in an agate ball mill jar for 60min. Load the mixture into a corundum boat and place it in a carbonization furnace. Introduce a mixed gas of oxygen / N2 (oxygen volume fraction of 5%) at a gas flow rate of 200mL / min. Heat the mixture to 250℃ at a heating rate of 15℃ / min and perform oxidation carbonization treatment for 60min. Allow it to cool naturally to room temperature, then remove it and crush it to a particle size of 50μm to obtain the second material.

[0062] The second material was mixed evenly with 11 g KOH, placed in a corundum boat, and put into an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 500 mL / min for 20 min. Then, the temperature was increased to 850℃ at a nitrogen flow rate of 500 mL / min and kept at a constant temperature for 100 min. The heating was then turned off, and the material was cooled to room temperature and taken out as the third material.

[0063] Weigh 4.4g of second asphalt and 0.88g of NaOH, mix them with the third material, and pulverize them together to a particle size of 30μm. Then, ball mill the mixture in an agate ball mill jar for 30 minutes. The mixture is then placed in a corundum boat and placed in an activation furnace. The air in the activation furnace is replaced with nitrogen at a flow rate of 500 mL / min for 20 minutes. The temperature is then increased to 600℃ at a nitrogen flow rate of 500 mL / min and maintained at this temperature for 60 minutes. The heating is then turned off, and the mixture is cooled to room temperature. This is the final activated product. The product is then filtered and washed with 5% dilute hydrochloric acid at a liquid-to-solid mass ratio of 10:1, followed by washing with ultrapure water at a liquid-to-solid mass ratio of 20:1. The resulting filter cake is dried in a 100℃ forced-air drying oven for 12 hours to obtain porous carbon. The porous carbon is ball-milled to a D50 of 6–10μm and then subjected to magnetic separation to remove excess metal ions, yielding petroleum-based supercapacitor carbon.

[0064] The petroleum-based supercapacitor carbon prepared in Example 2 was analyzed and tested, and its specific surface area was 536 m². 2The particle size distribution (D50) is 8.0 μm, with 88% micropores, 12% mesopores, and <180 ppm metallic impurities. Electrochemical testing showed that the device's specific capacitance was 11 F / g at a current density of 1 A / g, and the specific capacitance retention was 82% after 100,000 charge-discharge cycles.

[0065] Example 3

[0066] Weigh 2g of petroleum coke and 10g of first pitch and crush them to a particle size of 40μm. Then, ball mill them in an agate ball mill jar for 40min. Load them into a corundum boat and place them in a carbonization furnace. Introduce a mixed gas of oxygen / N2 (oxygen volume fraction of 2.5%) at a gas flow rate of 200mL / min. Heat the gas to 300℃ at a heating rate of 15℃ / min and perform oxidation carbonization treatment for 90min. Allow it to cool naturally to room temperature, then remove it and crush it to a particle size of 45μm to obtain the second material.

[0067] The second material was mixed evenly with 12g KOH, placed in a corundum boat, and put into an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 500mL / min for 20min. Then, the temperature was increased to 700℃ at a nitrogen flow rate of 500mL / min and kept constant for 90min. The heating was then turned off, and the material was cooled to room temperature and taken out as the third material.

[0068] 0.92 g of second asphalt and 1.84 g of KOH were weighed and mixed with the third material, then pulverized to a particle size of 30 μm. The mixture was then ball-milled in an agate ball mill jar for 50 min, placed in a corundum boat, and put into an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 500 mL / min for 20 min. The temperature was then increased to 800℃ at a nitrogen flow rate of 500 mL / min and maintained at this temperature for 20 min. Heating was then turned off, and the mixture was cooled to room temperature. This was the final activated product. The product was then filtered and washed with 5% dilute hydrochloric acid at a liquid-to-solid mass ratio of 20:1, followed by washing with ultrapure water at a liquid-to-solid mass ratio of 30:1. The resulting filter cake was dried in a 100℃ forced-air drying oven for 12 h to obtain porous carbon. The porous carbon was ball-milled to a D50 of 6–10 μm, with 75% micropores and 25% mesopores. Excess metal ions were removed using a magnetic separator to obtain petroleum-based supercapacitor carbon.

[0069] The petroleum-based supercapacitor carbon prepared in Example 3 was analyzed and tested, and its specific surface area was 1761 m². 2 The particle size distribution (D50) is 8.0 μm, and the metallic impurities are < 130 ppm. Electrochemical testing showed that the device's specific capacitance was 28 F / g at a current density of 1 A / g, and the specific capacitance retention rate was 81% after 100,000 charge-discharge cycles.

[0070] Example 4

[0071] Weigh 10 g of petroleum coke and 4.5 g of first pitch and crush them to a particle size of 30 μm. Grind them in an agate ball mill jar for 100 min, load them into a corundum boat, place them in a carbonization furnace, and introduce a mixed gas of air at a flow rate of 100 mL / min. Heat the mixture to 350℃ at a heating rate of 5℃ / min and perform oxidation carbonization treatment for 90 min. Allow it to cool naturally to room temperature (25℃, the same below), remove it, and crush it to a particle size of 30 μm to obtain the second material.

[0072] The second material was mixed evenly with 22 g KOH, placed in a corundum boat, and put into an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 500 mL / min for 20 min. Then, the temperature was increased to 850℃ at a nitrogen flow rate of 400 mL / min and maintained at a constant temperature for 50 min. The heating was then turned off, and the material was cooled to room temperature and taken out as the third material.

[0073] Weigh 1.6g of second asphalt, 3g of KOH, and the third material, mix and pulverize to a particle size of 30μm, then ball mill in an agate ball mill jar for 30min. The mixture is then placed in a corundum boat and placed in an activation furnace. The air in the activation furnace is replaced with nitrogen at a flow rate of 500mL / min for 20min. The temperature is then increased to 750℃ at a nitrogen flow rate of 500mL / min and maintained at this temperature for 30min. Heating is then turned off, and the mixture is cooled to room temperature to obtain the final activated product. This product is then filtered and washed with a 5% (w / w) dilute hydrochloric acid solution at a liquid-to-solid ratio of 15:1, followed by washing with ultrapure water at a liquid-to-solid ratio of 40:1. The resulting filter cake is dried in a 120℃ forced-air drying oven for 6h to obtain porous carbon. The porous carbon is ball milled to a D50 of 6–10μm, and excess metal ions are removed using a magnetic separator to obtain petroleum-based supercapacitor carbon.

[0074] The petroleum-based supercapacitor carbon prepared in Example 1 was analyzed and tested, and its specific surface area was 2432 m². 2 / g, particle size distribution D50 is 9μm, micropores account for 80%, mesopores account for 20%, and metal impurities are <160 ppm.

[0075] Electrochemical testing showed that the device's specific capacitance was 48 F / g at a current density of 1 A / g, and the specific capacitance retention rate was 91% after 100,000 charge-discharge cycles.

[0076] Example 5

[0077] Weigh 12 g of petroleum coke and 2.0 g of first pitch and crush them to a particle size of 30 μm. Grind them in an agate ball mill jar for 100 min, load them into a corundum boat, place them in a carbonization furnace, and introduce a mixture of oxygen / N2 (oxygen volume fraction of 10%) at a flow rate of 300 mL / min. Heat the mixture to 280℃ at a heating rate of 5℃ / min and perform oxidation carbonization treatment for 80 min. Allow it to cool naturally to room temperature (25℃, the same below), remove it, and crush it to a particle size of 30 μm to obtain the second material.

[0078] The second material was mixed evenly with 14 g KOH, placed in a corundum boat, and put into an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 500 mL / min for 20 min. Then, the temperature was increased to 800℃ at a nitrogen flow rate of 200 mL / min and maintained at a constant temperature for 80 min. The heating was then turned off, and the material was cooled to room temperature and taken out as the third material.

[0079] Weigh 1.4g of the second bitumen, 2g of KOH, and the third material, mix and pulverize them together to a particle size of 30μm. Then, ball mill the mixture in an agate ball mill jar for 30min. The mixture is then placed in a corundum boat and placed in an activation furnace. The air in the activation furnace is replaced with nitrogen at a flow rate of 500mL / min for 20min. The temperature is then increased to 900℃ at a nitrogen flow rate of 500mL / min and maintained at that temperature for 20min. Heating is then turned off, and the mixture is cooled to room temperature. This is the final activated product. The product is then filtered and washed with a 5% (w / w) dilute hydrochloric acid solution at a liquid-to-solid mass ratio of 15:1. The filtered product is then washed with ultrapure water at a liquid-to-solid mass ratio of 40:1. The resulting filter cake is dried in a 120℃ forced-air drying oven for 6h to obtain porous carbon. The porous carbon is ball-milled to a D50 of 6–10μm and then subjected to magnetic separation to remove excess metal ions, yielding petroleum-based supercapacitor carbon.

[0080] The petroleum-based supercapacitor carbon prepared in Example 1 was analyzed and tested, and its specific surface area was 1962 m². 2 / g, particle size distribution D50 is 8μm, micropores account for 81%, mesopores account for 19%, and metal impurities are <170 ppm.

[0081] Electrochemical testing showed that the device's specific capacitance was 39 F / g at a current density of 1 A / g, and the specific capacitance retention rate was 89% after 100,000 charge-discharge cycles.

[0082] Comparative Example 1

[0083] 10g of petroleum coke and 2.5g of first pitch were weighed and pulverized to a particle size of 30μm. The mixture was then ball-milled in an agate ball mill jar for 100min, and thoroughly mixed with 25g of KOH. The mixture was then placed in a corundum boat and placed in an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 500mL / min for 20min. The temperature was then increased to 900℃ at a nitrogen flow rate of 500mL / min and maintained at that temperature for 20min. Heating was then turned off, and the mixture was cooled to room temperature to obtain the activated product. The product was then filtered and washed with 5% dilute hydrochloric acid at a liquid-to-solid mass ratio of 15:1, followed by washing with ultrapure water at a liquid-to-solid mass ratio of 40:1. The resulting filter cake was dried in a 120℃ forced-air drying oven for 6h to obtain porous carbon. The porous carbon was ball-milled to a D50 of 6–10μm and then subjected to magnetic separation to remove excess metal ions, yielding petroleum-based supercapacitor carbon.

[0084] The petroleum-based supercapacitor carbon prepared in Comparative Example 1 was analyzed and tested, and its specific surface area was 1802 m². 2 The particle size distribution (D50) is 9 μm, and the metallic impurities are <200 ppm. Electrochemical testing showed that the device's specific capacitance was 31 F / g at a current density of 1 A / g, and the specific capacitance retention rate was 74% after 100,000 charge-discharge cycles.

[0085] Comparative Example 2

[0086] Weigh 10g of petroleum coke and 2.5g of first pitch and crush them to a particle size of 30μm. Then, ball mill them in an agate ball mill jar for 100min. Load the mixture into a corundum boat and place it in a carbonization furnace. Introduce a mixed gas of oxygen / N2 (oxygen volume fraction of 1%) at a gas flow rate of 200mL / min. Heat the mixture to 215℃ at a heating rate of 5℃ / min and perform oxidation carbonization treatment for 120min. Allow it to cool naturally to room temperature, then remove it and crush it to a particle size of 30μm to obtain the product.

[0087] The product was mixed evenly with 25 g KOH, placed in a corundum boat, and put into an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 500 mL / min for 20 min. Then, the temperature was increased to 900 °C at a nitrogen flow rate of 500 mL / min and held at that temperature for 20 min. The heating was then turned off, and the product was cooled to room temperature and removed as the activated product. The product was then washed by vacuum filtration with 5% dilute hydrochloric acid at a liquid-to-solid ratio of 15:1, followed by washing with ultrapure water at a liquid-to-solid ratio of 40:1. The resulting filter cake was dried in a 120 °C forced-air drying oven for 6 h to obtain porous carbon.

[0088] Porous carbon is ball-milled to a D50 of 6–10 μm, and excess metal ions are removed by magnetic separation to obtain petroleum-based supercapacitor carbon.

[0089] The petroleum-based supercapacitor carbon prepared in Comparative Example 2 was analyzed and tested, and its specific surface area was 2418 m². 2 The particle size distribution (D50) is 8.0 μm, and the metallic impurities are < 200 ppm. Electrochemical testing showed that the device's specific capacitance was 47 F / g at a current density of 1 A / g, and the specific capacitance retention was 69% after 100,000 charge-discharge cycles.

[0090] Comparative Example 3

[0091] Weigh 10g of petroleum coke and 2.5g of first pitch and crush them to a particle size of 30μm. Then, ball mill them in an agate ball mill jar for 100min. Mix them evenly with 25g of KOH, put them into a corundum boat, and place them in an activation furnace. Replace the air in the activation furnace with nitrogen at a flow rate of 500mL / min for 20min. Then, at a nitrogen flow rate of 500mL / min, raise the temperature to 900℃ at a rate of 10℃ / min and activate at a constant temperature for 20min. Turn off the heating, cool to room temperature, and take it out. This is the first activated product.

[0092] 1.8g of second asphalt and 3.6g of KOH were weighed and mixed with the first activation product, then pulverized to a particle size of 30μm. The mixture was then ball-milled in an agate ball mill jar for 30 minutes, placed in a corundum boat, and placed in an activation furnace. The air in the activation furnace was replaced with nitrogen at a flow rate of 500 mL / min for 20 minutes. The temperature was then increased to 700℃ at a nitrogen flow rate of 500 mL / min and maintained at this temperature for 30 minutes. Heating was then turned off, and the mixture was cooled to room temperature to obtain the final activation product. The product was then filtered and washed with 5% dilute hydrochloric acid at a liquid-to-solid ratio of 15:1, followed by washing with ultrapure water at a solid-liquid ratio of 40:1. The resulting filter cake was dried in a 120℃ forced-air drying oven for 6 hours to obtain porous carbon. The porous carbon was ball-milled to a D50 of 6–10μm and then subjected to magnetic separation to remove excess metal ions, yielding petroleum-based supercapacitor carbon.

[0093] The petroleum-based supercapacitor carbon prepared in Comparative Example 3 was analyzed and tested, and its specific surface area was 2187 m². 2 / g, particle size distribution D50 is 7μm, metal impurities <200ppm.

[0094] Electrochemical testing showed that the device's specific capacitance was 40 F / g at a current density of 1 A / g, and the specific capacitance retention rate was 81% after 100,000 charge-discharge cycles.

Claims

1. A method for preparing supercapacitor carbon, comprising the following steps: (1) The first material is obtained by mixing petroleum coke and first bitumen evenly; (2) In the presence of oxygen-containing gas, the first material obtained in step (1) is processed to obtain the second material; (3) After crushing the second material obtained in step (2), mix it with alkali and perform a first activation under an inert atmosphere to obtain the third material; (4) The third material, alkali and second pitch obtained in step (3) are mixed and activated twice under an inert atmosphere. After washing and drying, supercapacitor carbon is obtained.

2. The method for preparing supercapacitor carbon according to claim 1, wherein, The petroleum coke particle size in step (1) is 10–500 μm; the volatile matter content in the petroleum coke is 5 wt%–15 wt%.

3. The method for preparing supercapacitor carbon according to claim 1, wherein, The petroleum coke particle size in step (1) is 20–100 μm; the petroleum coke is petroleum coke with a fine mosaic structure.

4. The method for preparing supercapacitor carbon according to claim 1, wherein, In step (1), the weight ratio of the first bitumen to petroleum coke is 1:20 to 1:0.

1.

5. The method for preparing supercapacitor carbon according to claim 1, wherein, In step (1), the weight ratio of the first bitumen to petroleum coke is 1:10 to 1:0.

2.

6. The method for preparing supercapacitor carbon according to claim 1, wherein, The first asphalt in step (1) is one or more of petroleum asphalt and coal tar pitch, and the softening point of the first asphalt is 80 to 350°C.

7. The method for preparing supercapacitor carbon according to claim 1, wherein, The first asphalt in step (1) is petroleum asphalt; the softening point of the first asphalt is 100-300℃.

8. The method for preparing supercapacitor carbon according to claim 1, wherein, The oxygen volume fraction in the oxygen-containing gas in step (2) is 0.5% to 21%; the oxygen-containing gas is air and / or a mixture of oxygen and an inert atmosphere, and the inert atmosphere is any one or more of nitrogen, helium, neon, argon, krypton, and xenon.

9. The method for preparing supercapacitor carbon according to claim 1, wherein, The volume fraction of oxygen in the oxygen-containing gas in step (2) is 1% to 15%; the oxygen-containing gas is air and / or a mixture of oxygen and an inert atmosphere, and the inert atmosphere is any one or more of nitrogen, helium, neon, argon, krypton and xenon.

10. The method for preparing supercapacitor carbon according to claim 1, wherein, The processing time in step (2) is 20 to 200 minutes.

11. The method for preparing supercapacitor carbon according to claim 1, wherein, The processing time in step (2) is 60 to 120 minutes.

12. The method for preparing supercapacitor carbon according to claim 1, wherein, The processing temperature in step (2) is 80 to 350°C.

13. The method for preparing supercapacitor carbon according to claim 1, wherein, The processing temperature in step (2) is 100-300℃.

14. The method for preparing supercapacitor carbon according to claim 1, wherein, The base in steps (3) and (4) is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate, calcium hydroxide, and magnesium hydroxide.

15. The method for preparing supercapacitor carbon according to claim 1, wherein, The alkali in steps (3) and (4) is one or more of sodium hydroxide, potassium hydroxide, and potassium carbonate.

16. The method for preparing supercapacitor carbon according to claim 1, wherein, In step (3), the activation temperature is 700-1000℃ and the activation time is 20-120 min.

17. The method for preparing supercapacitor carbon according to claim 1, wherein, In step (3), the activation temperature is 700-900℃ and the activation time is 20-100 min.

18. The method for preparing supercapacitor carbon according to claim 1, wherein, The weight ratio of the second material to the alkali in step (3) is 1:0.2 to 1:

10.

19. The method for preparing supercapacitor carbon according to claim 1, wherein, The weight ratio of the second material to the alkali in step (3) is 1:0.5 to 1:

2.

20. The method for preparing supercapacitor carbon according to claim 1, wherein, The washing process in step (4) includes two steps: acid washing and water washing. The acid solution used in the acid washing process is one or more of hydrochloric acid, nitric acid, sulfuric acid, and acetic acid. The mass fraction of the acid solution is 0.5% to 20%.

21. The method for preparing supercapacitor carbon according to claim 1, wherein, The mass fraction of the acid solution is 1-10%.

22. The method for preparing supercapacitor carbon according to claim 1, wherein, The drying temperature in step (4) is 60-150℃ and the drying time is 1-24h.

23. The method for preparing supercapacitor carbon according to claim 1, wherein, The drying temperature in step (4) is 60-120℃ and the drying time is 4-12h.

24. The method for preparing supercapacitor carbon according to claim 1, wherein, The second asphalt in step (4) is one or more of petroleum asphalt and coal tar pitch, the softening point of the second asphalt is 80-200℃, and the content of metal impurities in the second asphalt is 20-300 ppm.

25. The method for preparing supercapacitor carbon according to claim 1, wherein, The second asphalt in step (4) is petroleum asphalt, the softening point of the second asphalt is 80-180℃, and the content of metal impurities in the second asphalt is 30-200 ppm.

26. The method for preparing supercapacitor carbon according to claim 1, wherein, The softening point of the second asphalt is 50 to 250°C lower than that of the first asphalt.

27. The method for preparing supercapacitor carbon according to claim 1, wherein, The softening point of the second bitumen is 100-200℃ lower than that of the first bitumen.

28. The method for preparing supercapacitor carbon according to claim 1, wherein, The weight ratio of the second bitumen to the first material in step (4) is 1:13 to 1:

2.

29. The method for preparing supercapacitor carbon according to claim 1, wherein, The weight ratio of the second bitumen to the first material in step (4) is 1:10 to 1:

3.

30. The method for preparing supercapacitor carbon according to claim 1, wherein, The secondary activation temperature in step (4) is 500–900℃, and the secondary activation time is 20–100 min.

31. The method for preparing supercapacitor carbon according to claim 1, wherein, The secondary activation temperature in step (4) is 600-800℃, and the secondary activation time is 20-60 min.

32. The method for preparing supercapacitor carbon according to claim 1, wherein, The weight ratio of the second bitumen to alkali in step (4) is 1:0.2 to 1:

10.

33. The method for preparing supercapacitor carbon according to claim 1, wherein, The weight ratio of the second bitumen to alkali in step (4) is 1:0.2 to 1:

2.

34. A supercapacitor carbon, wherein the supercapacitor carbon is obtained by the preparation method described in any one of claims 1-33.

35. The supercapacitor carbon according to claim 34, wherein, The supercapacitor carbon has a two-level pore system of mesopores and micropores, wherein the mesopore diameter is 2nm-5nm and the micropore diameter is 0.4nm-2nm. The mesopore volume accounts for 12-25% of the total pore volume, and the micropore volume accounts for 75-88% of the total pore volume.

36. The supercapacitor carbon according to claim 34, wherein, The specific surface area of ​​carbon in supercapacitors is 200-3300 m². 2 / g.

37. The supercapacitor carbon according to claim 34, wherein, The specific surface area of ​​carbon in supercapacitors is 1500-2500 m². 2 / g.

38. The supercapacitor carbon according to claim 34, wherein, The metal content of carbon in supercapacitors is no more than 300 ppm.

39. The supercapacitor carbon according to claim 34, wherein, The metal content of supercapacitor carbon is no more than 200 ppm.

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